Secondary recovery method for petroleum by fluid displacement



l-Gum \JWSS REFERENCE S. M. FOULKS SECONDARY RECOVERY METHOD FORPETROLEUM BY FLUID DISPLACEMENT Filed Aug. 20, 1959 2 Sheets-Sheet 1 O oQ a Q X 0 M AW X Mu 5 3 2 D 2 9 .m 0% O O 2 FIG.2

FIG.

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SIDNEY M. FOULKS INVENTOR. B @ww FIG.6-

TORNEY g- 4, 1954 .7 s. M. FOULKS 3,143,169

SECONDARY RECOVERY METHOD FOR PETROLEUM BY FLUID DISPLACEMENT Filed Aug.20, 1959 2 Sheets-Sheet 2 53 FIG. I! I I 4 I\@ o a 45. 5! 3 o O O SIDNEYM. FOULKS Fit? 7 MENTOR ATTORNEY 1 the procedure employed.

3,143,169 Patented Aug. 4, 1964 Eco 3,143,169 SECONDARY RECOVERY METHODFOR PETRO- LEUM BY FLUID DISPLACEMENT Sidney M. Fouiks. Irving, Tex.,assignor to Socony Mobil Gil Company, Inc., a corporation of New YorkFiled Aug. 20, 1959, Ser. No. 835,073 Claims. (Ci. l66--9) Thisinvention relates to the secondary recovery of petroleum from asubterranean formation and relates more particularly to the secondaryrecovery of petroleum from a subterranean formation by methods involvingdisplacement of petroleum within the formation by means of an injectedfluid.

Petroleum is usually recovered initially from most subterraneanformations as a result of gas pressure or natural water drive forcingthe oil from the petroleum-bearing formation. or reservoir, to aproducing well and to the surface of the earth. As recovery of petroleumfrom the formation continues, the reservoir energy gradually decreasesand finally becomes insufficient to force the petroleum to the surfaceofthe earth, although a major portion of the petroleum still remains inthe reservoir. To recover further petroleum from these reservoirs afterthe reservoir energy has begun to decline, secondary recovery methodsmay be employed. Various of these secondary recovery methods involvedisplacement of petroleum within the formation to a production, oroutput, well by injection of a displacing fluid, either a gas or aliquid. into the formation through an injection, or input. well.

In secondary recovery methods employing a displacing fluid, thedisplacing fluid travels from an injection well to a production well inpathways, other things being equal, determined by the number andrelative position of the injection and production wells. The petroleumwithin the pathways of travel of the displacing fluid in the formationwill be the petroleum susceptible of recovery by The remainder of thepetro- Igum. lying outside the pathways of travel of the displacingfluid. will not be recoverable by that particular procedure. The shapeof the area of the formation within the pathways of travel of thedisplacing fluid is termed the sweep pattern" and the ratio of the areawithin the sweep pattern to the total area is termed the sweepefliciency'. Practical operations, from the standpoint of Ill economy.require a maximum sweep efficiency commensurate with the number ofinjection and' production wells. Conventionally, the injection andproduction wells are arranged in regular, uniform patterns with aninjection well surrounded by a plurality of production wells. While highareal sweep efliciencies are obtained with these well patterns. stillhigher efliciencics are desirable.

It is an object of this invention to improve the extent of recovery ofpetroleum from a subterranean formation. It is another object of thisinvention to obtain a greater sweep efficiency in a secondary recoveryoperation employingadisplacing fluid. Further objects of the inventionwill become apparent from the following detailed description.

In accordance with the invention. in a secondary recovery operation forpetroleum oil wherein a displacing fluid is injected into a subterraneanformation through a central well and petroleum oil is displaced in thedirection of and produced from a plurality of wells surrounding thecentral well. there are provided two steps. In the lirst step. thedisplacing fluid is injected into the central well and petroleum oil isproduced from at least every one of the surrounding wells untilbreakthrough occurs at these surrounding wells. central well shut oil".the displacing fluid is injected into every other one of the surroundingwells and the petro- In the second step, with the lit) leum oil isproduced at the remainder of these surrounding wells.

FIGURES l and 2 are schematic diagrams illustrating an embodiment of theinvention.

FIGURES 3 and 4 are schematic diagrams illustrating the sweep patternsobtained with the embodiment of the invention illustrated in FIGURES land 2.

FIGURES 5, 6, and 7 are schematic diagrams illustrating otherembodiments of the invention.

FIGURES 8 and 9 are schematic diagrams illustrating the sweep patternsobtained with the embodiment of the invention illustrated in FIGURES 5and 6.

FIGURES l0 and II are schematic diagrams illustrating the sweep patternsobtained with the embodiment of the invention illustrated in FIGURE 7and FIGURE 6.

Referring now to FIGURE 1, field 20 overlying a pctroleum reservoir isprovided with a plurality of wells. These wells are arranged in aregular, geometric, uniform pattern. Further. each well is located atthe corners of a square. The pattern of the wells may also be 'describedas being such that any one well, a central well, is surrounded by eightwells equidistantly spaced from each other.

For purposes of simplicity and description, reference will be made inFIGURE 1, as well as FIGURES 2, 5, 6. and 7, to the wells within acircumscribed area. In FIG- URE I, this area is indicated by the numeral21. However, it will be understood that operations with respect to theother wells in the fields will be similar to those described withrespect to the wells in the circumscribed area. In the figures. a ringcontaining a central dot signifies an injection well, a solid circlerepresents a pro duction well, and a cross represents a well which hasbeen shut in.

In the circumscribed area 21 of FIGURE 1, well 22 is located at thecenter of the area. Located at the midpoint of each of the linesdescribing the circumscribed area are wells 23. 24, 25, and 30,respectively. Located at the four corners formed by the intersections ofthe four lines describing the circumscribed area are wells 31. 32, 33,and 34. respectively.

In the first step of the process, displacing fluid is injected intocentral well 22. In this first step, petroleum oil is produced fromwells 23, 24, 25. and 30. Thus, these wells are operated as productionwells. Additionally, in the first step, wells 31, 32, 33, and 34 areshut in.

The displacing fluid injected into well 22 passes through the petroleumreservoir underlying the field into the direction of the wells 23, 24,25, and 30. The pathways of the displacing fluid migrating from the well22 to any one of the wells 23, 24, 25, and are affected by the presenceof each of the wells to each other. Many of these pathways arecurvilinear and, thus, portions of the reservoir other than those in adirect line between well 22 and any one of wells 23, 24, 25, and 30 areswept by the displacing fluid. With continued injection of thedisplacing fluid into well 22, breakthrough of the displacing fluid intoeach of wells 23, 24, 25, and 30 eventually occurs.

With breakthrough of the displacing fluid into each of the fourproduction wells, the shape of the area swept by the displacing fluid.i.e., the sweep pattern. will be as indicated in FIGURE 3. This sweeppattern is the dark area 35 within the circumscribed area 21. The ratioof the area 35 to the area 21 varies with the ratio of the mobility ofthe displacing fluid to the mobility of the displaced fluid. Mobility isdefined as the ratio of the permeability of the reservoir to the fluidand the viscosity of the fluid. With a mobility ratio of 1:1, the area35 will constitute 45.5 percent of the area 21. Thus, with the wellpattern illustrated in FIGURE 1, the area swept by the first step of theprocess, with a mobility ratio of 1:1, will be 45.5 percent of the totalarea of the reservoir lying between the wells.

In the second step of the process, referring to FIGURE 2, central well22 is shut in. Wells 23, 24, 25, and are operated as injection wells,and wells 31, 32, 33, and 34 are operated as production wells. Theinjection wells will now be located at the midpoints of the linesdescrib ing the circumscribed area 21 and the production wells will belocated at the intersections of the lines describing the circumscribedarea 21.

The displacing fluid passes through the formation from each of theinjection wells into the direction of the production wells. Petroleum isproduced from each of the production Wells and eventually breakthroughof the displacing fluid occurs at each of the production wells. Thepathways of the displacing fluid migrating through the formation areaffected by the injection and production wells and many of the pathwaysare accordingly curvilinear. The sweep pattern at breakthrough followingthe second step of the process is as indicated in FIGURE 4.

Referring to FIGURE 4, the sweep pattern is the dark area 40. The majorportion of the circumscribed area 21 is included within the area 40. Theonly portion of the circumscribed area not included is the two smallareas located near each of the output wells 31, 32, 33, and 34. Theratio of the area to the area 21 will depend upon the mobility ratio.With a mobility ratio of 1:1, the area 40 .will constitute 91 percent ofthe area 21. Thus, with the well pattern illustrated in FIGURES I and 2,the total area swept by the procedure of the invention for a mobilityratio of 1:1 will be 91 percent of the total area of the reservoir lyingbetween the wells.

Another well pattern is illustrated in FIGURE 5. Field 41 overlies apetroleum reservoir and, similar to field 20, is provided with aplurality of wells. These wells in field 41 are also arranged in aregular, geometric, uniform pattern. Further, each well is located atthe corners of a hexagon. The pattern of the wells may also be describedas being such that any one well, a central well, is surrounded by sixwells equidistantly spaced from each other.

Well 42 lies in the center of circumscribed area 43. Located at theintersections of the six lines describing the circumscribed area arewells 44, 45, 50, 51, 52, and 53, respectively. In the first step of theprocess, displacing fluid is injected into central well 42. Petroleum isproduced from wells 45, 51, and 53 and, thus, these wells are operatedas production wells. Wells 44, 50, and 52 are shut in during this firststep. The pathways of travel of the displacing fluid are, as previouslydescribed, affected by the various wells and many of the pathways arecurvilinear. At breakthrough of the displacing fluid into productionwells 45, 51, and 53, the sweep pattern is as illustrated in FIGURE 8.The sweep pattern is the dark area 54 within the circumscribed area 43.For a mobility ratio of 1:1, the area 54 will constitute 53 percent ofthe circumscribed area 43.

In the second step of the process, referring to FIGURE 6, central well42 is shut in. Wells 44, 50, and 52 are operated-as injection wells andwells 45, 51, and 53 are continued to be operated as production wells.Displacing fluid is injected into each of the injection wells 44, 50.and 52 and petroleum is produced from production wells 45, Si, and 53.Many of the pathways of travel of the displacing fluid are curvilinear,as previously explained, and at breakthrough of the displacing fluidinto the pro duction wells, the sweep pattern is as illustrated in FIG-URE 9. The sweep pattern is the dark area 55 within the circumscribedarea 43 and the only portion of the circumscribed area not includedwithin the sweep pattern is the area 56. The sweep pattern willconstitute, for a mobility ratio of lzl, 86 percent of the circumscribedarea 43.

It will be noted that portions of the circumscribed area drive, miscibleflooding, and in-situ combustion.

43 included within the sweep pattern 54 are not included within thesweep pattern 55. This is due to displacement of petroleum oil duringthe second step of the process into a previously swept area. Thus,petroleum oil, following the completion of the first step of theprocess, remains in the vicinity of the shutin wells 44, 50, and 52.With operation of these wells as injection wells in the second step ofthe process, however, a portion of this petroleu'm oil is displaced intopreviously swept area 54.

The well pattern illustrated in FIGURE 5 may be operated in anothermanner. This manner of operation is illustrated in FIGURE 7. In thefirst step, central well 42 is operated as an injection well and wells44, 45, 50, 51, 52, and 53 are operated as production wells. Thedisplacing fluid is injected into central well 42 and it advancesthrough the formation to each of the output wells. Production ofpetroleum oil is from each of the production wells and some of thepathways of flow between the injection and production wells arecurvilinear. At breakthrough of the displacing fluid into the productionwells. the sweep pattern is as illustrated in FIGURE 10. The sweeppattern is the dark area 57 within the circumscribed area 43. The darkarea constitutes 74 percent of the circumscribed area 43, for a mobilityratio of 1:1.

The well pattern illustrated in FIGURE 1 may be operated in the samemanner as just described for the well pattern illustrated in FIGURE 5.Thus, displacing fluid may be injected into central well 22 and wells23, 34, 24, 31, 25, 32, 30, and 33 may be operated as production wellsin the first step. In the second step, central well 22 is shut in andeither wells 23, 24, 25, and 30 operated as injection wells and wells31, 32, 33, and 34 operated as production wells or wells 31, 32, 33, and34 operated as injection wells and wells 23, 24, 25, and 30 operated asproduction wells.

In the second step, operations are as illustrated in FIG- URE 6. Centralwell 42 is shut in. Wells 44, 50, and 52 are operated as injection wellsand wells 45, 51, and 53 are operated as production wells. Displacingfluid is injected into wells 44, 50, and 52 and it advances through theformation in pathways, some of which are curvilinear, to wells 45, 51,and 53. At breakthrough of the displacing fluid into the productionwells, the swgep pattern is as illustrated in FIGURE ll. The sweeppattern is the dark area 60 within the circumscribed area 43. The sweeppattern constitutes practically percent of the circumscribed area.

The procedure of the invention is applicable to any type of productionoperation for petroleum oil where a displacing fluid is injected intothe oil-containing information. Among these procedures are gas drive.water In gas drive operations, a gas such as a flue gas, carbon dioxide.natural gas, or other gas is injected into the formation into aninjection well. This gas displaces the petroleum 011 as it advancesthrough the formation and forces the oil through the formation into thedirection of the production wells. In water drive operations, water isinjected into the formation into an injection well and the injectedwater displaces petroleum oil from the formation and drives it throughthe formation to the production wells. In miscible flooding, a materialis injected into the formation through an injection well to form a fluidphase in the formation and thereafter a driving gas is injected into theformation. The material injected into the formation is one which ismiscible with the petroleum oil in the formation and the driving gas isone which is miscible with the material forming the fluid phase. Thedriving gas forces the fluid phase through the formation into thedirection of the production wells and the advancing fluid phasedisplaces the petroleum oil from the formation and drives it into thedirection of the output wells. In situ combustion, acombustion-supporting gas is injected into the formation through aninjection well and combustion of petroleum oil within the formation isinitiated.

With continued injection of the combustion-supporting gas, a flame frontadvances throughthe formation consuming a portion of the petroleum oilin the formation and displacing the remainder from the formation andforcing it into the direction of the production wells. Variouscombinations of these procedures may be employed. For example, gas andwater may be employed as the displacing fluid. Water may be used inconnection with a miscible flooding procedure. Water may also beemployed in conjunction with an in-situ combustion operation.

in the practice of the invention, it is not necessary that all the wellsrequired to carry out both steps be provided at the time the first stepis carried out. Those wells not employed in the first step need not beprovided until the second step is carried out. Thus, wells 31. 32. 33,and 34 of FIGURE 1 and wells 44, 50, and 52 of FlGURE 5 need not beprovided while the first step is carried out.

, During the time that the first Step is being carried out, or

after the final step has been carried out, these wells may be drilledand the second step thereafter carried out.

Having thus described my invention, it will be under stood that suchdescription has been given by way of illustration and example and not byway of limitation. reference for the latter purpose being bad to theappended claims.

I claim:

1. A process for the recovery of liquid material from a subterraneanformation penetrated by a central well surrounded by n peripheral wellsarranged in a geometric pattern with said central well at the midpointof said geometric pattern, each of said peripheral wells beingequidistantly spaced from each of the adjoining peripheral wells whereinn is a whole even number of at least 6, comprising the steps of:

(1) closing off every other of said peripheral wells.

(2) injecting into said central well a fluid capable of displacing saidliquid material contained within said subterranean formation,

(3) producing said liquid material contained within said subterraneanformation from the remainder of said peripheral wells until saiddisplacing fluid arrives at said peripheral wells,

(4) closing off said central well,

(5) opening said wells closed off in step (I).

(6) injecting into each of said peripheral wells opened in step (5) saidfluid capable of displacing said liquid material contained within saidsubterranean formation, and

(7) producing said liquid material contained within said subterraneanformation from the remainder of I said peripheral wells. 2. A processfor the recovery of liquid material from a subterranean formationcomprising thesteps of:

(l) drilling a well from the surface of the earth to said formation,

(2) drilling n peripheral Wells from the surface of the eath to saidformation arranged in a geometric pattern surrounding said first namedwell, with said first named well being located at the midpoint of saidgeometric pattern, each of said peripheral wells being equidistantlyspaced from each adjoining peripheral well and wherein n is a whole evennumber of at least 6.

(3) closing off every other of said peripheral wells,

(4) injecting into said first named well a fluid capable of displacingsaid liquid material contained within said subterranean formation.

(5) producing said liquid material contained within said subterraneanformation from the remainder of said peripheral wells until saiddisplacing fluid arrives at said peripheral wells,

(6) closing off of said first named well,

(7) opening said wells closed off in step (3),

(X) injecting into said wells opened in step (7) Said fluid capable ofdisplacing said liquid material contained within said subterraneanformation, and

(9) producing said liquid material contained within said subterraneanformation from the remainder of said peripheral wells.

3. A process for the recovery of liquid material from a subterraneanformation penetrated by a central well surrounded by six peripheralwells arranged in a hexagon with said central well at the midpoint ofsaid hexagon comprising the steps of (1) closing off every other of saidperipheral wells.

(2) injecting into said central well a fluid capable of displacing saidliquid material contained within said subterranean formation,

(3) producing said liquid material contained within said subterraneanformation from the remainder of said peripheral wells until saiddisplacing fluid arrives at said peripheral wells,

(4) closing off said central well,

(5) opening said closed peripheral wells,

(6) injecting into each said peripheral well opened in step (5) saidfluid capable of displacing said liquid material contained within saidsubterranean formation, and

(7) producing said liquid material contained within said subterraneanformation from said peripheral wells from which liquid materialcontained within said subterranean formation was produced in step 3 4. Aprocess for the recovery of liquid material from a subterraneanformation comprising the steps of (1) drilling a well from the surfaceof the earth to said formation,

(2) drilling six peripheral wells arranged in a hexagon surrounding saidfirst-named well with said firstnamed well being located at the midpointof said hexagon,

(3) closing off every other of said peripheral wells.

(4) injecting into said first-named well a fluid capable of displacingsaid liquid material contained within said subterranean formation,

(5) producing said liquid material contained within said subterraneanformation from the remainder of said peripheral wells until saiddisplacing fluid arrives at said peripheral wells,

(6) closing off said first-named well,

(7) opening said closed peripheral wells,

(8) injecting into each of said peripheral wells opened in step (7) saidfluid capable of displacing said liquid material contained within saidsubterranean formation. and

(9) producing said liquid material contained within said subterraneanformation from said peripheral wells from which said liquid materialcontained within said subterranean formation was produced in step (5).

5. A process for the recovery of liquid material from a subterraneanformation comprising the steps of (l) drilling a well from the surfaceof the earth to said formation,

(2) drilling three peripheral wells from the surface of the earth tosaid formation each located at alternate corners of a hexagon with saidfirst-named well being located at the midpoint of said hexagon,

(3) injecting into said first-named well a fluid capable of displacingsaid liquid material contained within said subterranean formation,

(4) producing said liquid material from each of said peripheral wellsuntil said displacing fluid arrives at said peripheral wells,

(5) closing off said central well.

(6) drilling three peripheral wells from the surface of the earth tosaid formation each located at the remaining alternate corners of saidhexagon,

(7) injecting into each of said last-named three peripheral wells saidfluid capable of displacing said liquid material contained within saidsubterranean formation, and

(8) producing said liquid material contained within said subterraneanformation from said first-named three peripheral wells.

References Cited in the file of this patent UNITED STATES PATENTS1,826,371 Spindler Oct. 6, 1931 3 Heath May 2, 1944 Jenks May 5, 1959OTHER REFERENCES Herold, S. C.: Some Analytical Principles in Recoveryby Force Drive, Oil and Gas Journal, Oct. 28, 1926, pp. 118, 171-174.

Fagin, K. M.: Effect of Well Spacing on Water Flood Operations andEconomics," Petroleum Engineer, June UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3 143 169 August 4, 1964 Sidney MFoulks It is hereby certified that error appears in the above numberedpatent requiring correctionand that the said Letters Patent should readas corrected below.

Column 1 line 68, before "one" insert other column 2 line 24, for "and"read of column 4 lines 50 and 51' for "information" read formation line73, for ""situ" read in-situ column 5 line 57, for "eath" read earthcolumn 6, line 34L after "wells" insert from the surface of the earth tosaid formation Signed and sealed this 8th day of December 1964 (SEAL)Attesi:

ERNEST -W. SWIDER' EDWARD J. BRENNER Aitesfing Officer A Commissioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No.3 l43 169 August 4 1964 Sidney Md Foulks It is hereb; certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column l line 68 before "one" insert other column 2 line 24 for "and"read of column 4 lines 50 and 51, for "information" read formation line73 for "'situ" read in-situ column 5 line 57 for "eath" read earthcolumn 6, line 34 after wells" insert from the surface of the earth tosaid formation Signed and sealed this 8th day of December 1964:,

(SEAL) Attest:

ERNEST w. SWIDER' EDWARD J. BRENNER iing ()fficer Commissioner ofPatents

1. A PROCESS FOR THE RECOVERY OF LIQUID MATERIAL FROM A SUBTERRANEANFORMATION PENETRATED BY A CENTRAL WELL SURROUNDED BY N PERIPHERAL WELLSARRANGED IN A GEOMETRIC PATTERN WITH SAID CENTRAL WELL AT THE MIDPOINTOF SAID GEOMETRIC PATTERN, EACH OF SAID PERIPHERAL WELLS BEINGEQUIDISTANTLY SPACED FROM EACH OF THE ADJOINING PERIPHERAL WELLS WHEREINN IS A WHOLE EVEN NUMBER OF AT LEAST 6, COMPRISING THE STEPS OF: (1)CLOSING OFF EVERY OTHER OF SAID PERIPHERAL WELLS, (2) INJECTING INTOSAID CENTRAL WELL A FLUID CAPABLE OF DISPLACING SAID LIQUID MATERIALCONTAINED WITHIN SAID SUBTERRANEAN FORMATION, (3) PRODUCING SAID LIQUIDMATERIAL CONTAINED WITHIN SAID SUBTERRANEAN FORMATION FROM THE REMAINDEROF SAID PERIPHERAL WELLS UNTIL SAID DISPLACING FLUID ARRIVES AT SAIDPERIPHERAL WELLS, (4) CLOSING OFF SAID CENTRAL WELL, (5) OPENING SAIDWELLS CLOSED OFF IN STEP (1), (6) INJECTING INTO EACH OF SAID PERIPHERALWELLS OPENED IN STEP (5) SAID FLUID CAPABLE OF DISPLACING SAID LIQUIDMATERIAL CONTAINED WITHIN SAID SUBTERRANEAN FORMATION, AND (7) PRODUCINGSAID LIQUID MATERIAL CONTAINED WITHIN SAID SUBTERRANEAN FORMATION FROMTHE REMAINDER OF SAID PERIPHERAL WELLS.